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PHYS 125 Fall 2007 Exam 1 Physics 125 Fall 2007: Exam #1 Form #1 Please print your name:_________________________________________ Please list your discussion section number:_________________________ Please list your discussion instructor:______________________________ Instructions • Fill in your name above. • Each exam will have a different version number which will need to be written in the area of the scantron marked “Form”. • Record all your answers on the answer sheet provided. • This will be a 1.5 hour, closed book exam. The exam includes 20 questions. • You may use a 3x5 note card containing information you think might be useful. You can write on both sides of the card if you like. • This is a closed-book exam. You may use a calculator which is for numerical calculations only and not to refer to stored information. • There is only ONE correct answer for each multiple-choice question. No partial credit will be awarded. • You may be asked to show your University student ID card when you turn in your exam. Discussion section reminder: Section 003 TUE/THUR 08:00-09:00 Salin Bernstein Section 004 TUE/THUR 09:00-10:00 Salin Bernstein Section 005 TUE/THUR 10:00-11:00 Salin Bernstein Section 006 TUE/THUR 12:00-13:00 Salin Bernstein Section 007 TUE/THUR 13:00-14:00 Salin Bernstein Section 008 TUE/THUR 14:00-15:00 Salin Bernstein Section 009 TUE/THUR 14:00-15:00 Konstantin Bobkov Section 010 TUE/THUR 15:00-16:00 Arthur Cole Section 011 TUE/THUR 16:00-17:00 Konstantin Bobkov Section 012 TUE/THUR 12:00-13:00 Andrew Tomasch Section 016 TUE/THUR 11:30-13:00 Arthur Cole Section 017 TUE/THUR 13:00-14:30 Arthur Cole Section 018 TUE/THUR 08:00-09:00 Andrew Tomasch Section 019 TUE/THUR 09:00-10:00 Andrew Tomasch 10/04/2007 - 1 - Form #1 PHYS 125 Fall 2007 Exam 1 1. A plane travels at a speed of 300 km/h relative to the ground at an angle of 30° north of east. The wind travels at a speed of 100 km/h relative to the ground at an angle of 60° north of east. What is the velocity, magnitude and direction, of the plane to the wind? A) 219 km/h, 16.8° north of east B) 219 km/h, 16.8° south of east C) 228 km/h, 18.4° north of east D) 412 km/h, 71.6° north of east E) 228 km/h, 18.4° north of east 2. For the figure shown below, which of the following are action reaction pairs? I) Force of friction of m 2 on m 1 and the force of friction of m 1 on m 2 II) The weight of m 2 and the normal force on m 2 III) The weight of m 2 and the weight of m 1 IV) The force of gravity on m 1 and force of m 1 on the Earth V) The normal force of m 2 on m 1 and the normal force of m 1 on m 2 A) I, II, V B) II, IV, V C) I, IV, V D) I, II, III, IV, V E) IV, V 10/04/2007 - 2 - Form #1 PHYS 125 Fall 2007 Exam 1 3. Find the magnitude of the force that mass m 1 exerts on mass m 2 if F = 900 N, m 1 = 10 kg, m 2 = 50 kg, and θ = 30°. Note: The force F is parallel to the incline and there is no friction between the incline and the masses. A) 750 N B) 900 N C) 260 N D) 230 N E) 615 N 4. A subway train starts from rest at a station and accelerates at a rate of 1.60 m/s 2 for 14 s. It runs at constant speed for 70.0 s and slows down at a rate of 3.50 m/s 2 until it stops at the next station. Find the total distance covered. A) 1467 m B) 1550 m C) 1674 m D) 1797 m E) 1856 m 10/04/2007 - 3 - Form #1 PHYS 125 Fall 2007 Exam 1 5. A pistol that fires a signal flare gives the flare an initial speed of 120 m/s. If the flare is fired at an angle of above the horizontal over the flat Sea of Tranquility on the moon, where g = 1.6 m/s 55° 2 , what is its horizontal range of the flare? A) 7,358 m B) 8,457 m C) 9,236 m D) 10,026 m E) 11,279 m 6. As two trains move in opposite directions along a straight stretch of track, their collision detection systems simultaneously notice that they are heading toward each other and automatically apply the brakes. The velocity curves for the two trains are shown in the graph below (using different line styles for each). Both detection systems activate at t = 0. What minimum initial separation must the trains have in order not to collide? A) 160 m B) 180 m C) 200 m D) 240 m E) 260 m 10/04/2007 - 4 - Form #1 PHYS 125 Fall 2007 Exam 1 7. An artist designs a fountain which is able to "shoot" short bursts of water from pipes placed around its edge as shown schematically below. Suppose the speed of the water is v as it leaves the pipes, which are inclined at an angle θ to the horizontal. You may assume that the burst of water have negligible length. If the distance between the pipes is d, what is the time t when the bursts of water first collide, assuming they are launched at the same instant? y A) 2 d t v = B) sind t v θ = C) tan d t v θ= D) 2cos d t v θ = E) cos d t v θ = 8. There is one force acting on an object. What can we definitely conclude from this? A) The object is going at a constant speed in a straight line. B) The object is speeding up or slowing down. C) The object has a constant velocity. D) The object is going at a constant speed, but not necessarily in a straight line. E) None of the above can be definitely concluded. 10/04/2007 - 5 - Form #1 PHYS 125 Fall 2007 Exam 1 9. A rocket in outer space (far from any gravitating bodies such as planets) accelerates at 30 m/s 2 when the engine fires. If the engine produces a thrust of 4500 N the rocket has a mass of: A) 110 kg B) 150 kg C) 190 kg D) 220 kg E) 310 kg 10. A crate rests on the flatbed of a truck that is initially traveling at 15 m/s on a level road. The driver applies the brakes and the truck is brought to a halt in a distance of 38 m. If the deceleration of the truck is constant, what is the minimum coefficient of static friction s µ between the crate and the truck that is required to keep the crate from sliding? A) 0.20 B) 0.30 C) 0.39 D) 0.59 E) This cannot be determined without knowing the mass of the crate. 10/04/2007 - 6 - Form #1 PHYS 125 Fall 2007 Exam 1 11. Think of how to describe the process of you jumping up in the air. In order to jump up from rest you must accelerate upward. Which of the following is a correct description of process by which you accelerate upward? A) The muscles in your legs push up on the floor creating a net upward force. B) You push down on the ground with a force whose magnitude is greater than the magnitude of the force of gravity on you. C) The magnitude of the force of the floor pushing up on you is less than the magnitude force of you pushing down on the ground. D) The magnitude of the force of the floor pushing up on you is greater than the magnitude force of you pushing down on the ground. E) The force of gravity does not act when you are in contact with the ground. 12. Two objects are attached to opposite ends of a string which is suspended from the two frictionless pulleys as shown below. Each of the objects has a weight of 5 Newtons. What is the tension in the string measured by the spring scale at the center? A) 0 N B) 2.5 N C) 5 N D) 7.5 N E) 10 N 10/04/2007 - 7 - Form #1 PHYS 125 Fall 2007 Exam 1 13. Captain Kirk and Mr. Spock are discussing the surface gravity of various planets. Captain Kirk notes that the planet Omicron-Seti 3 has a gravitational acceleration identical to that of Earth at its surface. Mr. Spock replies that the planet they are currently orbiting has five times the mass of Omicron-Seti 3 and three times its radius. The acceleration of gravity at the surface of the planet they are currently orbiting is therefore: A) 3.7 m/s 2 B) 4.3 m/s 2 C) 5.4 m/s 2 D) 6.9 m/s 2 E) 9.8 m/s 2 14. A pitcher delivers a fast ball with a velocity of 43 m/s to the south. The batter hits the ball and gives it a velocity of 51 m/s to the north. What was the average acceleration of the ball during the 1.0 milliseconds when it was in contact with the bat? A) 4.3 × 10 4 m/s 2 , south B) 5.1 × 10 4 m/s 2 , north C) 9.4 × 10 4 m/s 2 , north D) 2.2 × 10 3 m/s 2 , south E) 7.0 × 10 3 m/s 2 , north 10/04/2007 - 8 - Form #1 PHYS 125 Fall 2007 Exam 1 15. A spring-loaded gun is aimed horizontally and is used to launch identical balls with different initial speeds. The gun is at a fixed position above the floor. The balls are fired one at a time. If the speed of the second ball fired is twice the speed of the first ball fired, how is the horizontal range (denoted R in the figure) affected? A) The range for both balls will be the same. B) The range of the second ball will be half as much as that of the first ball. C) The range of the second ball will be twice as large as that of the first ball. D) The range of the second ball is about 1.4 times larger than that of the first ball. E) The range of the second ball will be smaller than that of the first ball by a factor of 1.4. 16. An eagle is flying due east at 8.9 m/s carrying a gopher in its talons. The gopher manages to break free at a height of 12 m. What is the magnitude of the gopher's velocity as it reaches the ground? Note: effects of air resistance are not included in this calculation. A) 22 m/s B) 18 m/s C) 11 m/s D) 9.8 m/s E) 8.9 m/s 10/04/2007 - 9 - Form #1 PHYS 125 Fall 2007 Exam 1 17. The graph shows the velocities of two objects of equal mass as a function of time. Net forces F A , F B , and F C acted on the objects during intervals A, B, and C, respectively. Which one of the following choices is the correct relationship between the magnitudes of the net forces? A) F B = F C > F A B) F C > F B > F A C) F A > F B = F C D) F A = F B = F C E) F A > F B > F C 18. Which expression is false concerning the vectors shown in the sketch? C B A A) C = A + B B) C + A = –B C) A + B + C = 0 D) C < A + B E) A 2 + B 2 = C 2 10/04/2007 - 10 - Form #1 PHYS 125 Fall 2007 Exam 1 19. Larry, Moe and Curly are hoisting a barrel of bricks (mass M=175 kg) using a light rope passing over a frictionless pulley attached to the ceiling. Larry and Curly begin to argue and both let go of the rope as Curly pokes Larry in the eyes with his fingers. With what acceleration is poor Moe (m=59 kg) dragged upward toward a painful collision with the ceiling? A) 2.9 m/s 2 B) 3.7 m/s 2 C) 4.3 m/s 2 D) 4.9 m/s 2 E) 5.7 m/s 2 20. A vendor is weighing bananas (m=5 kg) using a scale suspended from a rope tied to the branch of a tree. In an attempt to steal the bananas, a monkey in the tree pulls on the cord, hoisting the scale with the bananas upward with an acceleration of 3 m/s 2 . As his scale and bananas disappear upward into the tree, the vendor notes that the scale reads: A) 31 N B) 46 N C) 51 N D) 56 N E) 64 N 10/04/2007 - 11 - Form #1 Licensed User 1

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